Active vibration-isolating device

Abstract

The active vibration-isolating device of the invention is used for preventing vibrations due to ground motions or running of an automobile from being propagated to a platform which is disposed in, for example, a semiconductor device factory or a laser device factory, and on which various kinds of equipment are to be mounted, and also from causing the platform to vibrate. The device has: an air spring which elastically supports a platform; a piston-like member which abuts against and supports the platform; plural piezoelectric actuators which can be externally controlled; a working fluid such as an aqueous solution of ethylene glycol which transmits driving displacements of the piezoelectric actuators to the piston-like member via piston members which are respectively fixed to ends of the piezoelectric actuators in a driving direction x; and a fluid path in which the working fluid is hermetically filled. The load of equipment mounted on the platform is shared by the air spring and the piston-like member, thereby enabling the spring rate to be reduced. Therefore, the resonance frequency can be set lower. As a result, vibration-isolating performance and vibration-damping performance can be surely adequately exerted on vibrations in a wide frequency range including a low-frequency region, and a wide load range.